The present invention pertains to screens which provide shade and/or save energy. More in particular, the invention pertains to fire retardant, drapable screens for use in conservatories or greenhouses, mainly screens that partially consist of thin and flexible plastic strips that can be converted into a large, flat and pliable product, such as a fabric, in particular by weaving, using one or more yarns, if necessary.
Such screens are frequently used for protecting plants, in the open field or indoors in greenhouses, for controlling the incoming and outgoing radiation energy to a certain extent, so that the plants are protected against too strong sunlight and against too high or too low temperatures. Said screens, also called curtains, are spread vertically and/or horizontally over very large areas, with areas of 30,000 m2 not being exceptional. Because the plants to be protected may represent a great value, protecting them serves a major economic purpose. Usually, opening and closing the screens is done by electric means, with the screens being moved to the active or inactive position by means of motors.
In such environments a fire may start, for example in the case of the electric defects, during repair work involving grinding or welding, or of vehicles moving under the screen in the greenhouse. It has been established that such fires can spread very quickly over large areas via the screens. The fires constitute a danger to personnel present in the greenhouses, and can be destructive to the greenhouse itself and also to its contents.
Such screens for greenhouses are disclosed, for example in EP 0 696 884 B1, which discloses a screen comprising flexible strips consisting of a halogen- or phosphorus-containing plastic film, preferably made of PVC, PVDC, PCTFE, PVF, FEP, PTFE, E/TFE or PETP, which also comprises a UV stabiliser, at least partially laminated with a metal film and connected into a continuous product by crocheting or weaving, using a yarn system, said yarn system at least partially consisting of a flame retardant material, such as modacryl yarns. The strips as well as the yarn system are at least partially made of materials which are flame retardant or not easily flammable.
WO 2011/096882 A1 discloses a greenhouse screen comprising strips that are connected with a yarn system by means of hosiery, knitting, warp-knitting or weaving process, wherein the screen comprises multilayer polyester strips having a thickness less than 60 μm and wherein at least one layer of the multilayer polyester strips is white and at least one layer is black.
WO 2013/117696 A1 discloses a flame retardant screen comprising strips having a thickness of at most 100 μm, which are connected by flame retardant yarns. Hardly any flame retardants are incorporated in the strips which are made of a plastic having a limiting oxygen index of at least 18%, contain at most 0.15 wt. % of phosphorus, contain at most 900 ppm by weight of chlorine, fluorine or bromine, and contain at most 1.0 wt. % of sulfur. The only mentioned type of polymer of the strips is polyester.
EP 2 457 436 A1 discloses a shading screen made from fire resistant halogen-free polymer films, optionally laminated with a metal film, wherein the halogen-free polymer is polycarbonate, polycarbonate-polysiloxane block-copolymer or a blend of polycarbonate and polysiloxane.
XLS OBSCURA REVOLUX A/B+B/B, as sold by AB Ludvig Svensson, comprises two separate fabrics, wherein the top fabric comprises, in the machine direction, tapes of PVC laminated with Aluminum foil warp-knitted together with transparent modacryl yarns and with fire retardant polyester yarns. The lower fabric comprises, in the machine direction, tapes black polyester tapes warp-knitted together with fire retardant polyester yarns.
Regarding the fire properties of plastic objects, reference is usually made to the fire tests of DIN 4102, part 2 and part 1, or to the fire test of UL 94. Because said tests do not correspond very well to the actual fire behaviour of screen materials used in greenhouse farming, the new technical agreement NTA 8825:2010 was developed, which is specifically aimed at the fire behaviour of screen materials for use in greenhouses. The requirements in accordance with said agreement are being imposed in the most important markets in Western Europe. However, it has proven to be very difficult to meet the NTA 8825:2010 fire test requirements.
It is an object of the invention to provide screens for greenhouses that comply with the NTA 8825:2010 fire test requirements.
This and other objects are achieved by the screen described herein.